How do you deal with people who practise double standards?

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By that I mean like for instance people who tell you not to do something when they themselves do it. It's quite disgusting really. E.g. A coworker who tells you not to do ___, when you only did it once in your entire life, and after the first time she told you not to, you never did it again... but she herself continues to do that very same thing over and over again! It just pisses me off each time I see her do it, and I feel like telling her, didn't you once tell me not to do that? But I'm a non-confrontational person. All this has been silently simmering within me. I'm afraid one day things will turn ugly, or I'll go insane. Would appreciate hearing your opinions.